text:
Why couldn't the A380 secure any orders for two straight years?
The double-decker aircraft has failed to win a single order from any new airline customer for two years now. Comparing its orders and sales with its biggest competitor, the B747 it had received 315 orders in its first 10 years, about 40 years back. Today though, the A380 has recieved 317 in its first 8 years, but it failed to receive even a single order in past two years.

“It’s true the market hasn’t developed as much as we’d have liked,” Airbus Chief Executive Officer Fabrice Bregier said this month. “This plane was probably launched 10 years too early.” (Source)

Why couldn't the A380 sell as much as the B747, even though it has won many admirers in a shorter period of time. Also, a rough comparison shows A380 is worth its price, when compared to 747-8. But the 747-8 is still getting more orders than the A380.
Update : Iran Air has finally ordered some A380s in February 2016.

"But the 747-8 is still getting more orders than the A380." Not much more. Both aircraft are selling miserably.

Forty years ago, 315 aircraft over ten years was a much larger share of a much smaller market than 317 aircraft over 8 years is now. Then, global airlines were essentially British Airways, Pan Am, and a small number of national carriers, and long haul aircraft were mostly 707's and DC-8's and such; now EVERYBODY has a national airline with 777's and A330's, so as a percent of the market, 315 then was highly successful.  Big fish, small pond.  Today, the same size fish (raw sales #) in a far larger pond doesn't look so big, and many fear the A380 market is now topped out as well.

Regarding the close votes, I rather disagree that this question is primarily opinion-based. While some opinion may factor into the answers, as far as I know, the economic advantages of twins over quads are pretty well established, as is the general move towards twins among airlines for the last few decades.

A380 is too large and business passengers prefer more frequent service rather than more luxury service.

Look at the news that airlines refuse to buy A380 and you will know more about the reasons.

Your comparison between the A380 and 747-8 is not apples to oranges - the 747-8 has a freighter version, and the majority of orders have been of that variant.  The A380 does not have a freighter version at present.  If you compare A380 orders / deliveries to those for the 747-8 passenger variant only (747-8I), you will find the A380 is far ahead.

@NateEldredge - Which IMHO was one of Airbus's bigger mistakes with this airframe, essentially snubbing UPS and FedEx completely in order to fulfull obligations to its bigger customer Emirates. While Emirates responded with an additional 50 orders beyond the 90 it was waiting for, those delays also resulted in Emirates ordering more 777s as they'd be ready sooner, and UPS and FedEx ended up buying Boeing 767 and 777 ERF variants. Airbus simply could not get the airframes to market fast enough to keep the demand coming, and ended up scaring away billions in business.

The link shared in the question shows that the A380-800 had secured 13 orders in 2014. In 2015, there are no orders as on October 31, 2015. Cannot understand why OP is referring as to no orders in past two years?

Okay.. Rounding it to the nearest integer.

Alternately, you may edit the question the way you want to.

Here's a video which compares the business models of airlines buying big planes to airlines buying small planes. https://www.youtube.com/watch?v=NlIdzF1_b5M

Several reasons:

A380s are really expensive. Unit cost for an A380, depending on interior appointments, is about \$375 million. The 747-8 is about \$357 million. The 777-300ER is about \$320 million, the last variants of the A340 about \$275 million, and the 787 about \$200 million. The 380 might be the biggest airliner ever to fly, but it's also the most expensive. Keep in mind these jets can't fly every day, requiring you to buy a couple more than the schedule requires and rotate them in as maintenance is required on each airframe. That means A380 operators have at least one three hundred and eighty million dollar airframe sitting on the tarmac not making money on any given day (in fact, up to 55 days at a time for the 6-year "D check" maintenance, not counting lower-level maintenance performed more often as well as any unscheduled maintenance).
Airbus could not/cannot build them fast enough to meet initial orders in a timely manner. Airbus received 189 initial A380 orders prior to the airframe's scheduled start of production in 2007, plus 27 A380F variant orders, and has received 128 since production began (though the freighter orders were cancelled). To date, it's only delivered about half due to a combination of issues found during full-scale production that delayed ramp-up, and currently its pace is about 30 planes a year, giving it about a 3 year backlog of remaining orders (some of which have been sitting in the build queue for 10 years). It initially prioritized passenger variants for Emirates, which put in the largest single order (almost half of total orders) to handle that airline's primarily long-haul schedule. As a result, everyone else got pushed off until many (including FedEx and UPS which were waiting for freight versions) cancelled their orders and went to Boeing for 747-8Fs or 777-ERFs.
Jumbos represent a serious cost-revenue risk that most airlines are no longer willing to gamble on. You use a jumbo jet when you need to move a lot of people at one time. That typically means a high-demand, long-distance route that calls for nonstop service, but that you don't want to have to fly any more times than you have to. 747s used to be used for high-volume domestic connectors in the US during and immediately after the regulation era, between major cities like New York, Chicago, LA, Houston, Miami etc. They were also used for major intercontinental flights, primarily because regulations required more than two engines for trips extending a certain distance beyond the nearest divert field. However, the 747 is a 50-year-old design with only incremental improvements made in efficiency. Four engine jets in the modern air transport market require you to fill the plane every time, and with ETOPS-rated two-engine widebodies now making many of the same flights that previously required three or more engines, the A380, even with the most efficient engines ever put on a commercial airliner, is at least three decades late to the jumbo party, and is entering the market at a time when the 747 is being phased out of most fleets in favor of more economical widebodies.
The A380 was designed for an air travel market that hasn't materialized. Airbus was betting big (NPI) on airport congestion and increased passenger counts during the 80s and 90s requiring a shift to fewer flights on larger-capacity planes to reduce pattern and gate congestion. Except for a few major metropolitan areas that simply cannot grow their airports anymore (O'Hare, LaGuardia/JFK, Heathrow etc) that hasn't really been the case. 9/11 and the 2008 financial crisis have seen passenger counts plummet from post-regulation highs, which has reduced total flights and allowed smaller planes which are more efficiently scheduled. In addition, Denver opened up the largest airport by land area in the world (so it has plenty of room to grow), while Atlanta, Dallas, Charles de Galle and others are busy primarily because they're massive complexes with efficient layouts that can support a major airline's hub operations. The use of jumbos in general is therefore very risky, and many airlines, in addition to passing on the A380, are phasing out the venerable 747 that was previously unchallenged in this class, in favor of something a little more economical in the next smaller widebody class, like the 777, 787, A340 or A350. That was Boeing's bet, that smaller, high-efficiency jets would be the wave of the future over pure size, and it seems to be paying off as Boeing, despite higher production capacities, has more 787 orders than it has capacity for the foreseeable future, while Airbus's competing A350 is more or less getting the overflow (and it can't even meet that demand; 700 orders, 5 produced).
The A380 really doesn't solve the problem it was created for, and in fact causes more problems for airports than it solves. A super-heavy like the A380 creates monumental wake turbulence that poses a danger to other planes, which requires ATC to space following traffic further back (up to double the time/distance compared to a midbody), while for smaller jets (even widebodies), approach control can usually get away with a little more than standard 2-minute spacing unless the plane behind it is a much smaller regional jet or GA prop. So, the A380 can carry about 520 passengers in mixed-class configuration (Emirates' 6-star config seating only about 490), but takes up two "slots" in the approach pattern, while a 777 can carry 320 passengers in mixed-class layout and can be spaced much more closely to other airliners. So in terms of maximizing total passenger movement at an airport, two 777s or A340s are better than one A380.
At the gate, the A380 causes even more headaches. It's so honkin' big that adjacent gates typically can't be used while it's parked, and it often requires additional jetways to efficiently board and deplane its passengers. As one example, DFW's Terminal D was fairly recently renovated to be the airport's primary international terminal, including Gate 16 in the southwest corner specifically intended to allow 747s to park with minimal adjacent gate disruption (17 couldn't be used, but 18 was available for smaller jets and 15 around the corner could handle pretty much any size):

When the A380 came to DFW in 2014, with Qantas replacing the 747 on the famous Flight 7 and Flight 8 from Sydney to DFW (the longest scheduled passenger flights by travel time in the world), and Emirates commencing service to and from Dubai with A380s, DFW had to redesign this corner of the airport entirely, basically having the A380 come in diagonally to Gate 15. Gate 15 then services first class, 16's jetway was moved and extended to load and unload the lower deck, and a third jetway, 16X, was built adjacent to 16 solely for the A380's upper deck. The jetways for Gates 14 and 17 then had to be lengthened considerably to allow their use with a 380 at the ramp, otherwise the superjumbo would essentially take up 4 entire gates while parked:

As an aside for scale in the last image, Gate 14 to the right is in Sun Country livery which would make it a 737-700, while the American jet at the very top at Gate 19 is still in older livery, and with its long narrow body the best guess is a 757-200. Gate 17 looks like an Air Canada Rouge so with the body length I'd say A319, and Gate 18 is in new American livery so it's a 737-700. None of them really big aircraft by today's commercial standards, but they're certainly not puddle-jumpers either (all aircraft at this terminal are for international flights), and the Emirates A380 at gates 15/16/16X absolutely eclipses them all. It is a big jet.

"Denver opened up the largest airport by land area in the world" The land area of the airport is largely irrelevant. Most of the 53 square miles of Denver airport is unused space: the operational area fits in less than a quarter of the total.

Also, it was 3 engines that were required before ETOPS, not 4. Hence the DC-10 and L-1011.

@DavidRicherby The point was the airport has room to grow; add terminals, add runways, whatever it needs for more capacity. O'Hare can maybe add one more runway (and not a long one), Heathrow is pretty much done growing though there are plans to add a third runway, and Bloomberg's backing a plan to rebuild LaGuardia in place because that's the best way to get land for taxiways to relieve its congestion problems.

I will edit for pre-ETOPS regs.

Holy Concorde dejavu, Batman!

One of the most comprehensive answers I have seen on the exchange

Holy hell. One plane costs over 300 million?!

Yep. The scale of revenues and expenses for major airlines is truly massive. Some things to keep in mind though, the airliner is a 25-30 year investment. Each A380 running Qantas Flight 7 (and the return Flight 8) makes one round trip in two days (17 hours each way plus loading/unloading time), during which it carries up to 484 people each way, each of which pay a minimum of $988 one-way (PE, Business and First all pay way more; FC is $18,525 round-trip, Business $11,376, Premium Economy $4,446).

A full Qantas A380 for which everyone pays the current market price will earn the airline $1,876,134 per round trip. Each plane can do this run in two days, so in a year the plane earns the airline $342 million in ticket revenue, almost paying for itself in one year in raw earnings. Of course, fuel costs, flight crew salaries, maintenance and overhead eat away at that raw income, but Qantas still posted a $560 million net profit after taxes in 2014, more than enough to pay cash for a new A380 each year if it so desired.

It's not as fuel-efficient as a twin engine aircraft and doesn't offer as much scheduling flexibility.
Comparing the 747 in 1969 to the A380 today isn't really a good comparison. A better comparison would be comparing both of them today. In 1969, the 747 was revolutionary. It was the first large jet that could get a lot of people from one side of the world to the other relatively quickly and efficiently (compared to the previous-generation 707, DC-8, etc.) At that time, having either 3 or 4 engines was required by law for flights operating more than 60 minutes away from the nearest suitable diversionary field (in FAA-land, at least,) so it was a must for any aircraft that wanted to operate long-haul routes. However, as my answer here discusses further, the introduction of ETOPS in the 1980s and 1990s allowed twin-engine aircraft to start operating those routes. Since that time, the era of 3-engine and 4-engine airliners has been quickly drawing to a close.
Nowadays, airlines can get the same number of passengers from point A to point B using less fuel on large twin-engine aircraft while also gaining the ability to offer more flexible schedules (by spreading those passengers out between multiple daily flights) and better ability to match the number of seats on a route to demand on the route. Additionally, less engines means less maintenance costs. The A340 was the first major casualty of this effect, but it's killing the 747 and A380 programs, too. Meanwhile, Boeing and Airbus can't make 777s, 787s, A330s, or A350s as fast as they can sell them.
Here's what Wikipedia currently lists for open orders on the above types:
4-engine airliners:
Boeing 747-8: 31 unfilled orders
Airbus A380: 152 unfilled orders (which are mostly old and some of which may be cancelled)
Twin-engine airliners:
Boeing 777: 563 unfilled orders
Boeing 787: 803 unfilled orders
Airbus A330: 176 unfilled orders (I can't tell if this is also including the 145 A330neo orders)
Airbus A350: 776 unfilled orders.

This answer to the question about whether Airbus is planning to make a stretched A380 also contains some relevant information.

The B747-8 has a fuel economy of 90 mpg (per seat) whereas the 777-300 also gives approx the same. Both are calculated for a 3000 nmi range. What gives? Why do I not see the fuel economy difference between the 2 engine & 4 engine aircraft? Admittedly the B747-8 is 10 years younger but it also carries 100 more PAX. Your logic does make sense but I'm just curious why the data are not reflecting it.

@curious_cat Where are you seeing that data? Not that I'm doubting you; I'd just like to check it out. As you mention, though, the 777-300 is old. It's been out of production for quite a while now (and didn't sell particularly well even when it was in production, compared to the -200ER.) I'm sure on a per-engine basis the GEnx is more efficient than what was on the 773.

The newer 777 varients, e.g. 777-200LR and 777-300ER (first flights between 2003-2005) but they are shown to give a fuel economy of 72 mpg to 84 mpg per seat which is even worse. Even the 777-9X yet to be released is attributed only 84 mpg per seat. Something does not make sense to me. I am using data from this Wikipedia article: https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft Usually Wikipedia does a pretty reliable job at statistical facts so perhaps it is me who is making an interpretation error?

Another reason I used the older 777-300 to peg against the 747-8 is that they have a similar range of approx 3000 nmi. The newer 777 variants seem all extended range i.e. approx 7000 mi so it is obvious that they have a worse fuel economy per seat. Not an apples for apples comparison.

I even tried comparing the twin engined A330's that had a 3000 mile range versus the B747-8. The A330-200 and A330-300 are quoted an economy of 76 to 79 mpg per seat. Which is still worse than the B747-8's 91 mpg. Plus the 747-8 can haul 450ish PAX versus only 250 for the A330-200 and A330-300.

@curious_cat Hmm... the source for some of the 3,000 nmi trips seems to be an article titled "777 Way Much Better Than A330" and the source for the 747-8 3,000 nmi trip (as well as several of the others) claims to be a Boeing doc, but the link is dead.

Do you know of any alternative or more authoritative sources on airplane fuel economy? I'd love to cross check some of those suspicious figures. If the source is indeed the one you list then I'm not surprised it is biased.

@curious_cat There are some alternative sources, such as pilot forums, but they're not really authoritative, per se. In reality, real "mpg" numbers (not just in airliners, but in any airplane) will depend on pressure altitude, weight, wind, route, etc. This is why pilots usually use fuel burn per hour rather than directly fuel burn per nmi.

@curious_cat info I've seen shows the 747-8I having a range of ~8000nmi. Perhaps mpg at longer ranges drops, as the fuel fraction is larger?

@egid It does, but the source curious cited (some lists on Wiki) claims to be for the same distances. Having said that, the sources cited in Wiki itself seem to be less than authoritative.

@egid Don't the manufacturer's themselves publish indicative mileage figures? Or are they confidential data. I know they vary with altitude, weight etc. but they must have some way to benchmark this?

I highly doubt they all use the same benchmarks :) the big manufacturers have huge marketing and sales teams that I'm sure have the data.

When is the 747 planned to be dis-continued?

@Firee I'm not aware of any immediate plans to shut down 747 production, but with only 31 open orders and only 15 total net new orders since 2010 they won't be able to keep it going much longer without some significant new orders. Even at the rather slow delivery rates seen lately, that's only about 2 years worth of backlog.

The market for such a huge aircraft is very limited. The big airlines that have interest already have them. When the 747 was introduced, it was an unrivalled aircraft, and there was a booming market.
The A380 is now becoming a 10-year old aircraft in need of a bit of updating. The questionable outlook on orders does not inspire confidence in airlines that such change would take place.
The 747-8 orders are to some part passenger aircraft (many of the operators also with older versions of the 747, i.e. fleet commonality) but many are also freighter versions where there is nothing in that size category. Even so, the 747-8 is definitely not selling like butter, and they too have cut back production rates numerous times.

In a nutshell: The four engined jumbo jet as a airliner was killed by smaller ETOPS-certified twinjets with extended ranges.  The smaller twins are just more economical for the airlines and while slightly cheaper to buy new than a 747 or an A-380, they really beat the jumbos in terms of maintenance costs and airfield operation.
The 3- and 4-engined jumbo jets were the kings of the 1970s-1990s as engine technology during that period had not advanced to the point that reliability for extended overwater flights demanded an airplane with more than two engines onboard, justifying the extra operating costs associated with that design.  So as an operator faced with rapidly growing international air travel market and a choice between buying a 707 or DC-8 vs a 747, DC-10, or L-1011 and have the increased range and decreased operating cost per passenger mile combined with government regulation of the airlines to soften the financial blow in case the gamble didn't pay off for them, it made perfect sense to upgrade to the jumbo for their intercontinental operations.
In order to make its owner money, an airliner must be in the air with a full load of paying passengers going places.  Can't fill the seats because of travel demands?  Can't operate your jet from shorter airfields where your travelers are or want to go to nonstop?  Too bad.  You're going to lose money - and quite often a LOT of money on a failed gamble like that.  If you own or operate a jumbo jet you have to fly it like this round the clock, stopping only for passenger transfers, refueling, re-servicing and maintenance.  Periods of time where the aircraft is not doing this - even short ones - can cost the airlines literally millions of dollars in lost revenue with is why AOG is such a dreaded term.
With the dawn of the new millennium, air travel has changed.  Customer demands for long range, non-stop travel is more fluid and there is a greater profit to be made if you can provide the service from smaller satellite airports as opposed to limiting this to just the major hubs.  This combined with improvements in engine technology which made for the ETOPS-certification of twins for intercontinental routes and medium sized, extended range, twin wide body aircraft like Boeing's 767-300, 787 and the Airbus A350 fit much better into that niche, cost less both to buy and for the major budget buster of the airlines, the operating costs.
The operating costs of a 747 or an A-380 are similar to the costs of operating two A-330s or two 787s, except that its a single aircraft and cannot be rerouted depending on passenger loads.  The massive size of weight of the superjumbo jet (over 1.2 million lbs MTOW for an A-380!) requires long runways, wide taxiways with good clearance and parking ramps and gates which can accommodate the aircraft while the smaller jets fit better with established infrastructure at smaller airports, which gives a lot more flexibility for operations by the airlines to match passenger trends.  If travel demands change, simply re-route one or both aircraft to different fields by schedule.  Simple as that.
Bigger airplanes need more power, which means more fuel and maintenance per flight hour, mitigated somewhat by passenger loads.  Having a four engine aircraft adds a LOT more in maintenance costs, effectively doubling the op costs over a twin.  The dawn of the ETOPS twin made this apparent to the airlines and they quickly went over to medium-large twin engine aircraft for international travel.  This is strikingly obvious if you look at the orders for the A380's ancestor, the A340.  Sales for this airplane were quite strong in the 1990's but had decreased to a trickle by 2010 and beyond; I would be surprised if this aircraft was still in production by 2020.
There is one area where the superjumbo remains king of the air and that's in hauling freight.  Freight doesn't care much about hanging around airport terminals, changing planes and gates, flight delays, etc., so the hub-and-spoke and op cost per pound per mile advantages that a large aircraft like a 747 or A380 offers.  When I worked for Boeing as an intern in the summer of 2000, I only saw one passenger 747-400 on the lines; the rest were 747-400F freighters.  If you have ever watch the IMAX film 'Living in the Age of Airplanes', it quite convincingly advocates that our modern way of life would simply not be possible without these mechanical giants moving parts and parcels around the globe.

"Sales for this airplane were quite strong in the 1990's but had decreased to a trickle by 2010 and beyond." The latter part is quite an understatement while the former is an overstatement. There were only 6 of them delivered in 2010 and beyond, so there were likely no new orders placed during that time. The 777 killed the A340. After the first year the 777 entered production ('95,) there were more 777 deliveries than A340 deliveries every single year. In '99, the number of 777 deliveries was more than 4 times the number of A340 deliveries. By 2004, A340 production was in quick decline.

My point was more that the A340 didn't really ever have strong sales, even in the 90s. It was the wrong plane for the time, entering service only 2 years prior to the 777. Regarding the recent edit, I'd be surprised if the A340 were in production in 2020, too, since its production ended in 2012. :) Also, there is no freighter version of the A380 (there was one proposed, but it was never built.) But you're right that freight is the strong point of the 747. That's been even more true for the -8 than it was for the -400.

Put very simply it is an aircraft designed for a hub and spoke/star topology air network of main backbone routes connected to smaller regional routes,  launched at virtually exactly the time that carriers moved increasingly to direct point to point routes instead.
The backbone traffic that is there is already (over) serviced by existing 747 aircraft, there is very little need for new models of either beyond flagship aircraft. Instead long range ETOPS aircraft used on point to point travel are the major seller at present.
You could write a novel on WHY this move has happened - but it is at the core of the low sales of very large aircraft.
Also there are currently long waits for orders of the A380, so choosing one of the two you are likely to choose the one you can get.

Great question.  A380 and B-747 had nearly equal number of orders for the first 10 years.  Thereafter, for the B-747, orders jumped dramatically.  Will the A380 follow the pattern?  Probably not.  First, Boeing kept improving the 747 following its launch, delivering it in several models.  (In fact, its all-time best-seller, the 747-400, was still in the future.)  The A380 design has been stagnant.  Second, the B-747 had a huge advantage over its nearest competitors at the time (DC-10 and L-1011) in range - nearly 10,000 km for the initial version, v. 6000 for Douglas and 5000 for Lockheed (albeit numbers increased considerably for all over time.)  Simply put, the B-747 could fly routes that no-one else could.  While the A380 has superb range, it is not unmatched.  Studies have shown that number of seats per plane is largely unchanged over the past decade (or more), so capacity by itself doesn't sell planes.  Finally, Boeing designed the 747 from the beginning to be usable as a front-loading freighter.  Airbus has never mastered the concept.
Disclaimer - I have never owned or operated an airline.  Just interested in market dynamics.

A simple reason is that airlines have found another way to carry a large number of passengers at a smaller cost: the seat density.
Contrary to what was expected, the trend is not to sell more comfortable seats. This hits both Boeing and Airbus.
Why buy a gigantic Airbus A380 or Boeing 747 when you can squeeze more seats into a smaller plane instead?
This low-cost market trend coincides with the uncertain future of hubs at large airports, the trend being to see an increase in direct (and smaller) trips ratio.

Hmm... While I'm aware that AC and Lufthansa have been starting to use denser configurations, it seems that some other airlines have been doing the opposite. As the article mentioned Korean Air is one example of that, but even some of the U.S. carriers have started moving towards larger seats on their long-haul aircraft. Delta, for instance, is using a 3-3-3 configuration on their 777s nowadays. And the nicer SE Asian airlines mostly use the 3-3-3 configs with wider seats (and more pitch,) too. Delta has also moved to very nice seats in their business class (nicer even than Korean Air's.)

I'd say both situations are valid: Stuff more people in and sell a cheaper ticket on one flight (or class) for those who are price conscious while installing larger, more luxurious seats at a (much) higher price for those who are more concerned with comfort. Best of both worlds for the airlines.

Adding to others observations, the 747 has been around for so long that parts will be available for what I can see long after the 380 is no longer in  air. When the 747-8 rolled off the assembly line Boeing intentionally overloaded it to prove its heavy lift capability, something Airbus missed the boat on. The 380 was built on the CEO's ego. Boeing went with business logic with better performing smaller aircraft. I remember reading about Airbus betting on bigger and Boeing betting on smaller and which would be the correct choice. I think we know which was the correct bet.

Which was the correct bet? Neither one seems to be going very well.

@fooot Boeing's 'bet' was more on the 787 and 777. That bet has turned out quite well. Which Airbus also eventually figured out, hence the A350, which is also selling quite well.

authors: ابو عبدالحليم ال


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Even after years of research, why are planes unable to keep passengers alive in case of a fiery crash?
Aviation dates back to the 18th century, and since then tremendous research has been put into making aircraft safer and more efficient. Though these efforts have resulted in better aircraft, why are they still not strong enough to keep the passengers alive in case of a fiery crash?
In recent times, especially, it's a rare incident that a plane crashed and even some of its passengers survived. So, why has this issue not yet been resolved?

more strength means more weight, too much weight and you won't fly today.

@ratchetfreak A380 flies today!

You have this the wrong way round; its a rare incident when there is a plane crash and there are zero survivors! http://www.planecrashinfo.com/cause.htm

Err, 17th century? The Montgolfier brothers didn't fly the first balloon until the late late 18th (1783).

..it's even more rare for passengers to be killed by fire in a crash.  The crash itself, that leads to the fire, has already killed them.  To build any machine capable of withstanding the forces involved in the kind of crash you are talking about, as others had said, simply would not be able to fly.  Why haven't we built cars that will withstand any crash?  Or trains, or boats, or pedestrians surrounded with steel cages and impact absorbers?

@gochobot I meant as a play on "you will not go to space today" when a launch goes horribly/hilariously wrong on KSP

Humans have been walking for a looooooong time, yet they still trip and break limbs. You want 100% protection for them while they're encased in an aluminum tube buzzing along at 400+MPH 5 miles in the sky?

Actually, it's very rare for there to be any fatalities at all in modern airliners. Asiana flew a 777 into a seawall and the only fatalities were 3 (out of 300) people who got thrown out of the plane because they weren't wearing their seatbelts (and, even then, one of them died only because she was subsequently hit by a fire truck.) For the major U.S. airlines, there have been exactly 0 passenger fatalities in over 13 years, despite ferrying around several billion people during that time. Flying is one of the safest forms, if not the safest form, of transportation today.

I see a bunch of people talking about speeds like Mach .85, and the strength of cars vs. airplanes; so for reference, here's what happens to a car in a Mach .85 (950 feet/s) collision.

@Simon: "Why haven't we built cars that will withstand any crash?" -- We did, they're called tanks. But if you have a tank crash into a concrete wall at max speed, the tank will probably survive the impact, but the crew will definitely be out of action for a while....

Beyond a certain threshold, it's much more cost effective to reduce the likelihood of a crash than to improve survivability. As it is, crashes are very rare events in relation to the number of aircraft movements, flying hours, or passenger miles. There will always be non-survivable events in aviation, just as there are in road transportation; generally much easier to minimize the rate of event occurrences than reduce the proportion of them which are non-survivable.

Re-framing my previous comment: Aviation has advanced considerably over the past century. Among the many advances is the reduction in accident/incident rates, to the extent that unsurvivable events rarely ever happen now. Aircraft (yes, jet airliners) are safer in crashes than they used to be - improved restraints, fire safety, evacuation methods/systems etc. all contribute to improved survivability in certain types of incidents. But, the best accident to walk away from will always be the one that never happened.

@reirab That fact about passenger fatalities is remarkable! Do you have a source?

@KevinVentullo For the Asiana crash, the NTSB report has the details. Their website doesn't seem to be working at the moment, though, but there's always Wikipedia. For the point about the major U.S. airlines having no passengers deaths, check out AirSafe's list of U.S. airline crashes. The numbered crashes involved at least one passenger fatality. The most recent one involving any U.S. based non-regional airline was AA587, the A300 that crashed in Queens on November 12, 2001 where the vertical stabilizer separated.

@KevinVentullo For the number of passengers during that time, the U.S. Bureau of Transportation Statistics (yep, that's a thing) says that there were 9,586,996,000 passengers on U.S. air carriers from Dec 2001 through March 2015. While some of that is on the regional carriers, most of it is on the major airlines.

@KevinVentullo Another interesting fact: In that same time period, U.S. airlines have flown over 10 trillion revenue passenger-miles. To put that in perspective, that's about 112,000 times the distance from the Earth to the Sun.

Why crash more safely when you can simply crash less often? This way you save not only passengers but also the vehicle. This is exactly where all this research you've mentioned went: into not crashing.

Short answer
The kinetic energy involved in a plane crash is inhumanely high.
Slightly longer answer
We can built bombs which will go through concrete roofs and ceilings of a bunker, counting the number of floors they crash through while descending so they can explode at the level where the bad guys sit and not where the widows and orphans are kept. We could equally well build a plane with this kind of strength, so the fuselage stays intact even when it crashes into a mountainside. That's not the problem.
Limits of the human body
The problem will be that rescuers will only find dead bodies inside. The human body was "designed" to endure things like running into a tree, but not being hurled around at Mach 0.85 and then being stopped almost instantly. Thanks to years of research we now have quite a good idea where the limits are. Martin Eiband collected a lot of data on this, if you want to know more, google for "Eiband diagrams". If you want the full picture, read the Army Aircraft Crash Survival Guide. It comes in five volumes, and volume 1 covers the design criteria. The Eiband diagram below is lifted from this source.

Note the time scale: A deceleration with 40 g can only be tolerated for a duration of 0.1 seconds; if the deceleration takes more than 1 second, the limit is only 10 g. Now let's see what deceleration distance is required to stop a human with an average deceleration of 10 g. The energy $E$ of a body of the mass $m$ increases with the square of speed $v$:
$$E = m\cdot\frac{v^2}{2} = m\cdot a\cdot s$$
At $a = 98.0665$ m/s², the stopping distance $s$ from an initial speed $v$ is $\frac{v^2}{2\cdot a}$:

Car crash at 30 m/s: This needs 4.6 m and good restraints, but is generally survivable.
Free fall at 60 m/s terminal velocity: 18.4 m. A few humans have indeed survived this by falling into soft ground like a snow-covered conifer forest. This is also the typical approach speed of airliners, and the 18.4 m is the fuselage ahead of you. That is the reason why a crash is more survivable for the occupants in the rear seat rows.
Propeller airplane flies into mountain (120 m/s): 73.42 m. This kind of crumple zone is simply not available, and nobody has survived such an impact.
Airliner flies into a mountain (240 m/s): 293.7 m. To make such a crash survivable, every airliner would need to carry a 300 m boom of stiff material around which would be needed as a crumple zone in an accident. Just think what kind of aft fuselage and tail this would require.
And to top it: Astronaut on a space walk collides with a satellite in an opposing orbit (16,000 m/s): 1305.23 km. Note that I had to switch units to keep the number manageable.

Please consider lower deceleration limits for elderly and untrained persons; the limit in the Eiband diagram was established using healthy young pilots (and hogs, chimps and corpses for the higher limits. A lot of blood was spilled to arrive at these numbers).
The problem is not the aircraft structure, it is the fact that humans like to go fast but are not built to stop quickly.

That last sentence sums it up very nicely. One to remind.

I want to know who the human was at 200G & 0.015 sec, that looks rough.

@egid: Hard to say, but most likely John Stapp. The short time makes it more an acceleration spike, not continuous acceleration. If this kind of acceleration takes more than a tenths of a second, blood vessels may rupture internally. After suffering 200 g for 0.1 sec, the corpses look outwardly intact, but are a mess inside.

Yeah, makes sense!

Basically, to make all crashes survivable to the majority of people we'd have to pass a law forcing all planes to fly no faster than 44mph. Not only would most modern planes not be able to take off (indeed most WW1 biplanes would stall and crash at that speed) but most people would simply take the bus in that case.

So what are the chances of astronaut surviving the collision with the satellite ? :)

@NewbieProgrammer: Precisely zero; because as soon as your velocity drops so does your ability to orbit, and even if you might have somehow survived the fall, only very tiny and very crispy black pieces will have survived burning up in the atmosphere.

This assumes that the only way to crash-proof a plane is to make the plane itself crash-proof, "but people inside it die". Well, duh, of course this is not right way to do that. In future maybe there could be "alternate approaches" towards this problem, which might prevent the sudden deceleration in the first place. Obviously I don't know how, but still this answer is wrong, since it takes a wrong assumption, i.e. "there can't be any other way, and the specific obvious way doesn't work".

@Lohoris: The other way is never to speed up in the first place. Once you accelerate beyond a speed from which a human can be stopped safely, there will always be a nonzero risk - however small - that deceleration is lethal.

@PeterKämpf non-zero risk sure, but there might be several other ways to solve this problem. There aren't any now, but this doesn't mean the we should assume this will be the same in future.

Leave it to @PeterKämpf to delve into the physics, yet make it readable to mere mortals. Well done!

@PeterKämpf a very good answer.. But, KeithS's looks better.. Anyways, you have reached your daily max......

@Lohoris : the question asked about modern day airliners and our current understanding of physics, so using magic, a time machine, or popping up a wormhole in front of the aircraft would be off-topic.

@gochobot: I upvoted KeithS myself. No problem.

@MichaelT: Thanks for sharing the link! I enjoyed it much more than that story involving a fire extinguisher to de-orbit to the Chinese space station.

I thought that survival of high gees can be facilitated by pressurizing the passenger to many atmospheres (including making the passenger breathe oxygenated fluid). Not practical for ordinary commercial flight, but it is a possibility, no?

@RossPresser: New to me - I only remember studies to submerge pilots in a water tank to sustain higher gs in air combat, but this was to compress their body to equalize the higher blood pressure in the abdomen and legs. Works fine, but weighs much more than a g-suit. For deceleration such a method is new to me.

So, one way to enhance survivability is to reduce the crash velocity. One a flight emergency you can have a conflicting situation. The pilots may be trying to salvage the flight but worst case scenario is a crash and the optimal parameters for both cases are different. On the one hand the pilots may be trying not to stall and to maneuver and and hence keeping speed about their stall speed which can be quite high. On the other hand if a crash is imminent it might be crucial to use up those last seconds of flight with full air brakes and wheels and flaps etc. to get as much drag as possible.

Basically to continue to fly usefully you want speed. But to crash safely you want to kill speed. That decision might be crucial. To decide the plane will crash for sure and kill speed in the air. Even 10 secs more of in-air slowdown might mean more survival

@curious_cat: A popular way is to sideslip into the ground if all else fails, at least with small airplanes. This gives the speed killing effect you describe and has saved the rear end of a number of pilots. What also matters is the direction of flight speed - if it is parallel to the ground, the crash is much more survivable. Pilots will try to get the direction rather than the size of the speed vector right.

@PeterKämpf: Thanks! Interesting. Are there situations where pilots do not realize / conclude that a crash is imminent  and hence the need to side slip & align etc.? Are there crashes where to the end the pilot was hoping to salvage the plane? I speculate that these will be the most dangerous crashes from a survival POV  because the speed may very well be high or even increasing.

@curious_cat: In most crashes the pilot hopes for the best until the end, and humans have an innate tendency to stay with the craft - it provides also some protection, after all. And a controlled ground contact at higher speed might be preferable to an uncontrolled impact at a slightly lower speed. But it is hard to make generalizations - every crash is different.

Then how does Iron Man's suit protect him? :)

The link to the Army Crash Survival Guide is broken.

@SteveV.: Thanks for letting me know. I inserted a new link to Vol.1.

The Luke Aikins skydive-into-a-net might make a useful addition to the second bullet point. The 18.4m figure looks about right for the net's stopping distance.

@curious_cat To reduce crash velocity, can't we add various reverse thruster rockets to the aircraft fuselage, which acts in the same way when a rocket is trying to land on earth, it basically reduces the acceleration and also align in. I'm sure the experts here would be better able to elaborate my idea.

@curious_cat There have been several crashes in dense fog where airplanes/helicopters have flown into buildings or the side of a mountain. I've no idea how much actual warning they get in those cases but presumably not enough :(

@Firee yes, we could, but the added weight of toting them around on the 99.99(something)% of flights that don't need them (whether commercial or GA) significantly increases the cost of flying, as well as the cost of maintaining a system that's almost never going to get used...

The principal reason plane crashes are less survivable, which nobody really seems to fully grasp when talking about airliners, is the sheer amount of energy inherent in a commercial airplane. When you watch a plane coming in for approach, especially a big one like a 747 or A380, it usually seems very docile, with the plane very slowly and gently approaching the runway. The other classic image is the plane cruising at high altitude, perhaps leaving a contrail behind it as it slowly tracks across the sky. We compare these images from our experience to images of cars zooming past us along a busy road (or a racetrack). We then watch racecar drivers walk away from spectacular wrecks, while plane crashes kill everyone aboard, and we wonder why planes can't be made as safe as racecars (or even ordinary passenger cars).
That image of the docile aircraft traversing the friendly skies, however, is a forced perspective caused by a much bigger object much further away from us, and belies the fact that dozens or even hundreds of tons of weight is moving up to three times faster than an Indy car has even been clocked.
Basic projectile physics; $E = \frac{1}{2}mv^2$. The car in your driveway, if typical, has a "curb weight" (empty tank but otherwise ready to drive) of about a ton and a half, and cruises at speeds between 30 and 70 mph. Converting mph to fps (multiply by 5280, divide by 3600), the energy, in foot-pounds, of a 3000lb car at a freeway speed of 60mph is about 23 million foot-pounds, plus the additional kinetic energy of driver, passengers and cargo. In a collision, this energy is transferred wherever it will go; the object being collided with, the frame of the car, its occupants, etc. Even at these speeds, a collision can permanently injure or kill someone inside (and a full-speed collision on the highway is more often fatal than not).
A typical airliner, say the B737-700 which is in common use in the U.S. domestic fleet, has an "operating empty mass" (similar to "curb weight" in cars; everything needed to fly except the fuel and flight crew) of about 40 tons. So right there the potential energy of the airliner is 30-40 times the car. It also takes off and lands at roughly 125-150mph, and cruises at up to Mach 0.78, which at 30,000 ft is about 525mph. So, we're also talking about an order of magnitude difference in velocity, and that increases total energy on the square. Doing the math, an airliner at cruising speed, not counting the energy inherent in its cargo or passengers, will have a total kinetic energy somewhere on the order of 50 billion foot-pounds. Even with all other things being equal, such as the distance allowed for deceleration and the distribution of impact forces to the passengers, a passenger in a plane crash would be subjected to more than ten times the forces they would in a car crash.
Now, all these things can be mitigated in both cases. These numbers more or less compare what a passenger in a car vs a plane would go through if the vehicle plowed head-on into an immovable obstruction at full speed. That doesn't happen often in either case; highways are built in part to minimize the chance a driver will ever face a barrier head-on, and drivers can usually hit the brakes to slow the car and steer to hit in an oblique direction, and even if that won't prevent an impact it lessens the severity of it by the square of the change in relative speed between the car and what it's hitting.
Similarly, a CFIT (Controlled Flight Into Terrain) is pretty much the worst case scenario for a plane crash (the only worse one I can think of being a midair collision which is extremely rare especially for airliners), and there are a lot of systems aboard the aircraft to help a pilot realize he's about to do that. A crash landing, such as a belly landing due to hydraulic failure, is usually more survivable because the pilot is doing everything he can to minimize the force of impact and the plane's total kinetic energy, by both slowing the plane's forward velocity and reducing the glide slope. The plane's remaining kinetic energy can then be spent skidding down the runway or over the field instead of being imparted directly into the aircraft's frame and ultimately its passengers.
However, that's still a lot of energy for the plane to get rid of, and even with the inherent weight of an airliner, the ability to fly is favored by designers over keeping the cabin in one piece in a crash. That means that the inherently higher risk to life and limb of flying must be mitigated by keeping the planes well-maintained, and putting well-trained, experienced, healthy flight crews in them. Neither can be said for the average car and driver plucked off the street; only the most severe medical conditions are grounds for revocation of a driver's license, while most cars are driven thousands of miles past scheduled maintenance intervals. Cars, therefore, must be designed and built to keep the occupants alive in a collision, despite the ability or even the intentions of the driver. A plane's safety features are only useful when the pilot is doing his job properly; an oxygen mask or even an escape hatch is useless in a CFIT.

Very well said! Don't forget the common statistics that air travel is far safer (per passenger mile) than auto travel.

@FreeMan And just about every other form of travel, as well.

Safety in terms of deaths/injuries per passenger mile is actually a bit misleading, because planes cheat the calculation by logging up a lot of passenger miles quickly. The basic reason for safety of air travel versus anything else is the number of people in control as a percentage of the total number of people at risk. An airliner has two people in control of a plane carrying two hundred, and those two trained half their life to do that. In the U.S. there are 800 vehicles for every 1000 people so on average you can expect 1.25 people per car. That's way too many people making dumb choices.

@KeithS While I agree that limiting the chances for people to do stupid stuff is the primary reason that airliner travel is more safe than motor vehicle travel, that still doesn't change the fact that it's true. Of course, there is also a second important reason: for all but the first few minutes and last few minutes of a flight, there's usually nothing nearby that can be crashed in to. While cars operate several inches to a few feet from the nearest obstacles, airliners spend most of their time miles from the nearest obstacle - in all three dimensions.

Can't vote you up - you are distracted by the completely irrelevant (here) elements of mass, force, and momentum. It is sufficient to examine the kinetics for such a circumstance as Peter Kampf has done.

SI units, please. :-)

@KeithS - NIce analysis from an energy perspective... How do I know you are American? Because of all foot-pounds and bushels per groat? - no. Because you spelt kerb,  curb? - no. It's because you think an average car weighs a ton and a half!

@OwenBoyle A typical new-ish Ford Fiesta weighs about 1100-1250kg... some even more.  A Micra even pushes over 1000kg.  Consider also that 1.5 US tons is only 1360kg.  I would say that value is actually quite conservative, even for Europe (...or Asia, the former British colonies, or wherever else from whence you might be making that statement ;).

the ability to fly is favored by designers over keeping the cabin in one piece in a crash - nice risk assessment by the designers.

@KeithS Why is it cheating to logging up passenger-miles quickly?

Really? I don't think that a massive parachute for the whole plane or a massive airbag would add more than 2 ton for a plane....but if the weight is the problem then the question is...why we build planes with such heavy materials?

@KeithS: It's not "cheating", it's the exact definition of "passenger-mile".  You might prefer some other metric (for some strange reason), but this one is perfectly accurate and understandable.  Also while it is (reasonably) true that there are 800 vehicles for every 1000 people in the US (passenger vehicles, anyhow - there are actually somewhat more total vehicles), the rest of your math doesn't follow.  Given that there are more vehicles than licensed drivers, you cannot make simple assumptions about the number of occupants of a given moving vehicle.

In evaluating the force a passenger is subject to why is the plane's mass relevant? Shouldn't it be the passenger's mass? The overall deceleration times the passengers mass is the force he is subject to.

If you do the math using the passenger's weight and the speed of the car versus the jet, it works out about the same; velocity increases by an order of magnitude, which increases the energy by two orders of magnitude. I used the mass of the plane because figures were readily available, and because even a survivable plane crash requires bringing the entire plane to a halt, dissipating all that energy, without imparting fatal G-forces to the passengers.

The question is really a cost benefit analysis of assumed risk. You could fly planes with passengers that had full nomex suits on, a parachute, a back up chute, a life jacket, self deploying life rafts full of food and other neat survival gear. The plane could have a full frame chute, a steel roll cage and the best impact protection available. But all of this adds weight to the plane and thus reduces how many people you can fit. In turn you make less money per flight since its counter productive for flights to be impractically expensive no matter how safe. In the end of the day you alone can not move as far or as fast as a commercial plane nor do you have the resources to make an almost perfectly safe plane. So you compromise and assume risk for the reward of moving fast and semi efficiently.
On the contrary it should be noted that some people do have the resources to fly fast and safe. If you had the money to buy a small (or even big) plane you are free to outfit it (with in legal and practical/physical limits) as you like. This could include what ever protection you may desire from what ever emergencies you can think of.
One last note: its usually the emergencies you cant think of that are the real issues...

All this is true, and it still won't protect you from all possible contingencies. Flying into terrain at high speed will still cause fatalities for example.

In the words of Jeremy Clarkson "Speed does not kill, Sudden Deceleration does"

@GdD Not to be too pedantic (like James May), but you could account for that by making the flights go a lot slower.  In fact all dangers could probably be nullified if we took extreme measures to do so.  But, again, I don't think people would want to take these measures because it nullifies to much of the benefits of air travel.  People are okay with the current assumed risk, so they buy tickets...

Look at Payne Stewart and Air France #447 - all the safety gear in the world won't help if the autopilot goes nuts while the pilots are distracted and without a horizon, or if the cabin suddenly loses pressure while the pilots are out of their seats.

@PieterGeerkens Again, it's trade offs...but I continue to be pedantic.  You have to disregard, firstly, what we assume a plane to be.  Payne Stewart's plane would have been fine if they'd never gone above 10,000, and AF447 wouldn't have happened if people never flew through storms or at night.  But again, these are risks we are willing to take for the benefits they give us.  And that's the point being made here.  All risks can be mitigated. But achieving that would dilute the benefits so much...it's just not worth it.  We trade a small chance of death for a major benefit in mobility.

@JayCarr "you could account for that by making the flights go a lot slower." No you couldn't. A car crash at 60mph is already likely to cause fatalities. Airliners have to go twice that fast just to stay in the sky.

This answer assumes that you could reasonably equip an aircraft so most passengers survive.  However, as Peter Kampf  points out, the engineering here is prohibitively difficult, much more difficult than a "a full frame chute, a steel roll cage and the best impact protection available"  Also, see the question on frame chutes here: http://aviation.stackexchange.com/questions/9564/why-dont-big-commercial-planes-have-full-aircraft-parachutes  and on personal parachutes: http://aviation.stackexchange.com/questions/2186/why-are-commercial-flights-not-equipped-with-parachutes-for-the-passengers

One thing you could note to strengthen this "risk vs reward" task is that adding weight or taking up room in aircraft means fewer passengers can be carried in each plane and more planes are needed, which increases the number of accidents that will occur (thought the effect on probability of a crash per passenger is less straightforward).  Adding bulky safety features to planes means more planes in the air which means more crashes.

@DavidRicherby Not to mention that flight height is also involved - if you lose control of the craft and start falling, it doesn't matter what your flight speed was - you're still falling a few kilometers through the air. Lowering flight speed will only mitigate one risk - unexpected in-flight collision (i.e. flying straight into another plane or a mountain rising out of fog). This can be partially mitigated by other things, like the aerodynamics of the craft, but if (say) you lose a wing, you're dead. There's no practical flight height where that wouldn't be true regardless of flight speed.

Though these efforts have resulted in better aircraft, even then why are they not strong enough to keep the passengers alive in case of a fiery crash?

A fiery crash poses many challenges:
Physical
The occupants of the airplane are subject to a high acceleration the moment the airplane makes contact with the terrain. The human body can only sustain a dozen of g-force before sustaining internal damage.
Considering an airplane impacting horizontal terrain with a vertical speed of 1000 ft/min (5 m/s), and an airplane which the cargo space deforms one meter: going from 5 to zero m/s in the distance of 1 meter already results in a acceleration of 12.5 g (5 to zero m/s in 0.4 s) which is barely survivable.
Fire and fumes
An fiery crash would most likely rupture the fuel tanks, spilling the remaining fuel on-board and causing a fire which would release fumes rapidly incapacitating passengers.
Search and rescue deployment
As airplanes fly routes which have no connection with the ground road network, the time required by the search-and-rescue team to locate and reach the crash site is way too long for saving passengers requiring immediate medical help.

In recent times, especially, it's a rare incident that a plane crashed and even some of its passengers survived. So, why has this issue not yet been resolved?

Road accidents, were of the above three factors only the physical one can be considered, can already result in severe injuries and death.
With airplanes, traveling at a speed faster by one order of magnitude, it is easy to imagine that the consequences of a collision with the terrain are far more dramatic.

That last sentence is especially true considering that a speed increase of one order of magnitude yields a kinetic energy increase of two orders of magnitude. That's a lot of energy to dissipate very quickly. It's gotta go somewhere. Still, though, fuel ignition isn't all that common (in jets, at least) unless they really are flown straight into terrain. Despite the large fire that eventually burned up the plane after the Asiana SFO crash, for example, IIRC, the fuel never burned (an engine fire started the fire.)

If the cargo hold alone deforms one meter, the total stopping distance for the passengers is going to be more like two meters or so (at least), because of the give in the other parts of the aircraft between the ground and the passengers.

Because there is only so much acceleration and temperature a human body can survive.
The other answers provide detailed explanations how immense the energies of a crash can get, and how expensive it can get when you carry much less passengers because of the space needed by all the extra safety features.
However, there is another issue: the rarity of emergencies coupled with the probability of a correct decision regarding the case of an emergency.
Let's assume that money would not be an issue, and that we could install some very powerful systems which can increase the number of survivors in a crash, something like installing ejection seats for the passengers, full-frame parachutes or retro-rockets to slow down the aircraft or other far-fetched solutions like wrapping the whole aircraft explosively into a big bubble of some exotic material. These active countermeasures need to be very quickly deployable, so they would need to be triggered explosively. Even these solutions would not save everyone: for example, with ejection seats in military aircraft, there is an approximately 30% chance of receiving lasting injuries, and 10% chance of not surviving at all. With untrained passengers who are on average much less fit than fighter pilots, the survival rate would be lower.
However, you might say that if these countermeasures could save even just a few people, they are still better than everyone dieing in the crash? Wrong! We have to consider the likelihood of these countermeasures activating accidentally when there is no emergency at all! Not even counting cases where there is an emergency, but trying to ditch the aircraft onto a field or into a river might save more lives than activating the countermeasures.
The odds of being on an airline flight which results in at least one fatality are 1 in 3.4 million, and this counts even cases where the majority of the passengers survived. As the decision of activating the countermeasures has to be made at least once a couple of minutes (or maybe seconds) otherwise it would be too late, and the average airliner flight lasts between 3 to 6 hours, we have additionally at least 2 more orders of magnitude. This means that if you can make a correct decision about activating the emergency countermeasures with an accuracy of less than
99.999999997%, you will have more cases when they activate in a perfectly ordinary flight than in an emergency. Such an accuracy can not be expected from any decision making process, as accidents can have a wide variety of causes and are influenced by many factors from weather to mechanical failures to human psychology. As you can not even get near such an accuracy, such a system would likely kill many thousands times more passengers by activating when it shouldn't, than how many people it could save in actual emergencies.

Fire is lethal, in a crash and otherwise
It's people who keep the passengers alive
To answer your question directly, you survive a "fiery crash" by getting out of the aircraft, which is done by emergency evacuation.  For example, a fiery crash in Dubai recently resulted in zero casualties.  In contrast, the crash ofSwissair 111 all on board perished; a fire in flight turned from a bad situation into a lethal one.  The evacuation is run by the cabin crew, people who are trained on how to get people out of a crashed aircraft.
Fire is a seriously lethal problem to have, be it on a ship at sea, on an aircraft in flight, or after a crash.
For that matter, if you have a fire in your home you'll die if you don't get out, and that's without "a fiery crash."  (My wife's best friend lost her mom to a house fire: mom was asleep when fire started ... RIP.)
If a plane crashes, and it catches fire, and the fire can't be extinguished, and if you can't evacuate, you will burn and die.
A great deal of money, time and effort goes into accident prevention, an iterative process since the dawn of commercial aviation.  Improvements in the ability to evacuate in the case of accident or malfunction are included.
A great many other accident prevention systems have be put into place over the past century, which has paid off over time with the following goal: don't have the "fiery crash" in the first place.
An ounce of prevention trumps a ton of cure.

As it has been said, there is a lot of "cost" and "weight" in the reasons behind this. For small airplanes you have plane-parachute for example but how to make a suck system working for a 200-tons plane flying at 800km/h full of people ? There are real technical challenges behind this question.
Choices have been made to reduce the probability of a crash instead of adding some stuff to be crash-proof : electronics and hydraulics systems are redundant, emergency procedures, collision avoidance system, etc.
You also have to take into account that civil aviation is not fast evolving : adding some new technology requires long time to be tested, validated, and a good reason to add it. The usual flow of event in this case is : crash -> investiguation -> correct what's wrong -> wait for next crash etc...

Also people want other stuff like being awake- more air , eating, entertainment- that's priority over safety.

@user2617804 Given how many people complain about how uncomfortable and boring flying is and how bad the food tastes, compared to how many people complain about being in plane crashes, your statement is rather silly.

As for your answering the question about a 'fiery crash', NASA performed a test in the 1970s using a 720 filled with fuel formulated to reduce the chance of causing a fire. I recall seeing the footage on science programs. Unfortunately the fuel did ignite.
To quote the referenced Wikipedia article "The test resulted in a finding that the antimisting kerosene test fuel was insufficiently beneficial, and that several changes to equipment in the passenger compartment of aircraft were needed"

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text:
How does the in flight entertainment system works?
I board an aircraft, wait for it to takeoff, then find the headphones somewhere near my seat plug them into the two-pin point, and it works! But, how does it works for hundreds of other passengers simultaneously? Where is all the content stored, how are the screens connected to it, and how powerful is the computer controlling so many screens? Also, why is IFE required to be connected to aircraft's main computing system, which may eventually lead to the hacking of an aircraft?
Side Question : On an average, what is the size of content stored in a typical In-flight entertainment system?

Wikipedia has a page on ife, but surprisingly it doesn't explain its working!

How does this relate to aviation? On principle, this question is same as asking how does a cable provider broadcast contents to different subscribers.

then, why does the the ife tag exist? I mean, this is probably the most fundamental question about ife. Anyways, if you feel this is off-topic, I would delete this..

I think that your side question relates more to aviation than the main one. Let's see what the community thinks. But don't delete it, it can be improved.

I found a resource specifically for Emirates, so I'll try to explain it with respect to Emirates, though various other Airlines would use more or less the same principle.

Emirates uses Panasonic Avionics IFE (In Flight Entertainment) system.
  They have the 3000i which is older generation of IFE system on older
  aircrafts and the latest version ex2 on new aircrafts. Media licensing
  is managed, I believe, by the IFE provider via links to the major
  studios. In this tie up, the media is encrypted and stored in portable
  media loaders for the airline to update on the aircrafts. As the media
  is encrypted so the studio doesn't have much objection in giving away
  the rights to air the movies on board rather quickly.
The Portable media loaders use optical connection for faster data transfer to
  minimize the loading time.
The Main Aircraft Interface (AI) Server is nothing but a small
  computer which is generally called a LRU (Line Replaceable Unit) a
  small box which controls the entire IFE system of the aircraft the
  back end software can either be windows 95 or Linux depending on the
  type of system. 3000i uses windows. The movies are stored on other
  LRUs which are generally an array of Digital Data Servers or Media
  Servers (MS) or in lay mans terms Hard Drives! These are connected in
  a LAN network and ethernet IP addressing is used in the entire
  aircraft system.
The data is distributed over Optical fiber in first phase and over
  normal ethernet network to the specific seats. The interface is done
  via Ethernet Switches which intelligently routes the data from the
  Media server to the Area Distribution box to the Seat Electronic box
  and finally to the Smart Display.

Using a central dedicated computer instead of individual computers on different seats is preferred as it is less costly. Also, the IFE is connected to Aircraft's Main IFE cpomputer, and not the Aircraft's main computer, so by hacking it all you get is the files (IFE files), not the aircraft data, though the moving map system data might be first dumped into the IFE system from the Airplane's main computer

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text:
Are military and passenger jets insured?
Are aircrafts insured? Basically, I want to ask who bears the financial liability in case of some mishap? The airline company/government or some other company.

Passengers - yes: http://en.wikipedia.org/wiki/Aviation_insurance for more info.

Military (unsure hence non answer) - Very unlikely, would be very high premiums and would usually be cheaper not too.

In terms of liability, it depends what the mishap was. In most cases the insurers would cover the costs, but the liability may remain solely on the pilot.

okay.. but even then premiums would be very high for some aircraft like an a380, also which pilot would be so rich to take the liability of whole aircraft?

It would, however most airliners get fleet insurance, to cover all of their fleet. which reduces the cost. I also believe that commercial flights in planes such as an a380 must be insured.

I believe that ICAO rules mandate liability coverage on all civil aircraft. In fact, it is often the insurance company that poses the strictest conditions for the operation (stricter than the national aviation authority), for instance on crew training and experience levels required to operate the aircraft. And since the insurance is mandatory, if you can't fulfil their requirements, the plane can't fly (legally).

I'd be surprised if military combat aircraft are insured for damage or hull-loss. I doubt any insurer would insure combat missions. Large organisations can often self-insure (i.e. they have sufficient income to cover routine losses) and the military can almost always get additional one-off funding from governments for replacement costs during periods of high loss-rates (i.e. combat attrition).

In insurance industry, this is not the aircraft which is insured, but the person at the origin of the damage in which the aircraft is involved. The damage may be to the aircraft, to the crew, to the passengers, to other assets, to other persons, etc, and the insurance may cover the repair and/or the liabilities/damages for others. Application example: who is liable for an a eardrum perforation to a passenger traveling without a valid ticket ? Will an insurance cover this damage?

Commercial aircraft are insured in exactly the same way that companies insure other vehicles like cars. Broadly speaking, a company - the airline in this case - purchases hull insurance and liability insurance. The hull insurance covers damage to the aircraft and the liability insurance covers other costs like damage to property, medical payments, compensation to passengers and other costs caused by an event. Lloyd's of London has a useful summary. There are also all sorts of specialized insurance policies available to cover specific flights, aircraft, countries, cargoes etc.
Small private aircraft can be insured in the same way, although many owners of older, less valuable aircraft don't buy hull insurance because over a period of years the premiums can be more than the value of the aircraft. Most pilots do carry liability insurance, however, to cover medical or other expenses for themselves and their passengers (although in the US at least there's no requirement for pilots to have any insurance at all).
I don't know anything about military aircraft and it's a more complicated case: governments are typically immune from liability (at least, you can't sue them) so it really depends on the legal situation and practices in each country.

ya, you cant sue govt but the govt must have paid for the  aircraft, what about that money? Nice answer for passenger though!

You mean to cover the hull loss of govt aircraft? That money is usually called fiscal budget. And it comes from our tax money :)

As long as the government can tax its citizens, it will have no problem replacing a lost jet.

A partial answer for the case of military peacetime accidents: the government concerned seems to take responsibility for compensation - a few examples:

Cavalese cable car disaster (1998)
2012 Virginia Beach F/A-18 crash


text:
Are 360s by a B777 common in the holding pattern?
I found this forum having tried to find the answer on Google. I was on a B777 coming into Heathrow from Miami yesterday (AA56) and was expecting us to go into the usual hold. The attached picture showed we did ultimately do that but not after making a seriously tight circle. I thought at the time this was unusual in such a big plane so looked it upon flightradar (link below) and you can see just how sharp it was. Is this normal? I'm not the best flier so was pretty freaked out. I'm sure it's fairly common but I have never experienced anything like it, short or long haul.

https://www.flightradar24.com/data/flights/aa56#1069b0be

There's a number of questions on the site about Flightradar24, often involving its lack of accuracy. Consider Flightradar24 to be worth approximately what you pay for it, but do check out those other questions.

possibly duplicate of: https://aviation.stackexchange.com/q/2269/1467

Thanks for the reply.  Completely appreciate that but I can say from having been in the plane that it was a VERY sharp circle!

@Will There's no way whatsoever it was as represented there - that's a data issue.

Thanks! Yeah, I did appreciate it was exaggerated on the site. It has the plane turning completely within the lengh of a longish residential road! But just interested to know why we did such a tight circle rather than just going straight into a normal hold. As I say, it felt sufficiently weird for me to go online!

360s are quite common, but they're smooth circles. FR24 likely just got two points in this circle, making it look much more dramatic.

A standard rate turn is 120 seconds, or three degrees of turn per second. Taking @Sanchises' comment at face value, even that would be considered tight for an airliner, but I don't have any first-hand experience on that.

if the question is "why the 360" then is probably a duplicate of this: https://aviation.stackexchange.com/q/41006/1467 or this https://aviation.stackexchange.com/q/27789/1467
and the circle was not tight, given the data available, it was a 4km radius turn, with a bank angle of about 22°, well within the normal limits

@Sanchises the circle is south of those points, those points are a glitch

Thanks all! @Federico that circle to the South felt entirely normal but as mentioned we did another, much sharper turn before that. That is what is showing up on FR24 as well. Sure, it wasn't as tight as shown as that would be impossible but it was most certainly not the usual turn in a long haul flight.

I don't understand why this is being marked as a duplicate for inaccuracies of data on Flight Radar 24? The OP is asking if it's normal for an aircraft to do tight turns and uses a screengrab from Flight Radar to illustrate what happened on the aircraft he was on.

Thanks @BDLPPL - that's exactly what I was trying to find out!

The Flightradar data shows that your supposed "360" happened at 8:16UTC, and there are 4 datapoints with the same timestamps. Even being generous and allowing 15 seconds between one point and the next, it would translate in a turn with 300m radius and a bank angle of nearly 80°, sorry, but that's simply not possible.

Also Flightaware does not show any additional loop: https://flightaware.com/live/flight/AAL56/history/20180213/0010Z/KMIA/EGLL


text:
What indication will appear in case of one of A320 LGCIU is inoperative?
What indication and where it will appear in case of one of LGCIU (landing gear control and interface unit) is inoperative?

Could you maybe explain what LGCIU is and what aircraft you are talking about? I assume A320 Landing Gear Control Interface Unit since that is what shows up first on Google, but we cannot be sure.

you a right, yes a320, thank you. I've added the info

enter link description here
A320 ECAM "WHEEL" page
The answer:
The LGCIUs (landing gear control and interface unit) receive position information from the landing gear, cargo doors, and landing flap systems and process gear and door position, sequencing, control, and gear lever selection.
When one of two LGCIU is inoperative (№6) amber XXXs in the triangle - indicates that one LGCIU has failed.
...
Source: http://www.a320dp.com/A320_DP/landing-gear/sys-12.2.0.html

Could you provide attribution for the image?

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Can planes flap their wings like birds?

Birds use their strong breast muscles to flap their wings and give them the thrust to move throught the air and fly. In a way, birds use a swimming motion to get the lift needed to fly. Plane wings have a similar shape as bird wings, but instead of flapping their wings, we use engines to thrust them into the air and create the lift needed to fly. (Source)

Can we design an aircraft which could also "flap" its wings to fly?
Yes, we would need fuel to anyways do that.  But, from a design point of view, is it possible to do that?

They are called ornithopters

Does not seem to be much point?

It's a good evolutionary solution, needing only, er, evolution rather than revolution to go from limbs to flapping feathered limbs.  The main problem with fixed wings would be a source of propulsion.  A bird would have to eat a whole lot of chilli beans to generate that kind of thrust.

IIRC, there is no biomechanical equivalent of a rotating shaft and bearing, (so far).

@MartinJames I was thinking more along the lines of jet propulsion.  No moving parts required - just a good supply of beans.

There's also the whole biology thing, where you have lots of joints and flexible muscles that are self-repairing, with highly specific control & sensory systems (that is, nerves) for each muscle.  Which not only flap the wings, but are able to spread out individual feathers.  You might be able to build something similar, but it would be a nightmare to maintain.

They can... once.

From a biological point of view, flapping wings is a viable means of flight. However, this presents some problems when scaled up for human flight.
One issue is the square-cube law: as the wings are scaled up, the area scales as a square (relating to lift), but the volume scales as a cube (relating to weight). This means the wings increase in weight faster than they increase in lift, resulting in less effective wings. The higher weight presents issues in making them flap.
ratchet freak pointed out that we do have such machines, and they are called ornithopters. Although there is some potential at smaller sizes (for small UAV's), the weight and force issue prevents them from being very useful at larger scales. Ornithopters were some of the first unsuccessful designs for heavier than air flight.
The best solution we have found is propellers. This doesn't work as well as biological propulsion, but it's much easier to spin a prop than flap the whole wing, and works much better for the larger scales we need to move humans. Flapping is also not effective for reaching higher speeds.
You can also see from the biological side that there is a size limitation. The largest birds are much smaller than our airplanes.

There can be several reasons:

Airplanes' wings are huge and heavy. Birds' wings are light.
A bird's wings are flexible but an airplane's are not.
A mechanism to flap an airplane's wings will be a very complex process.
A lot more power will be required to flap airplanes' wings (even if flapping wings are designed successfully) than the current jet engines.
The flight will not be as smooth as it is now in airplanes, as a bird constantly moves up and down when it is flapping its wings. This can be seen in this picture of an ornithopte:

Did you spot this airplane flying in the evening sky?

An interesting article about this: Why don't airplanes have flapping wings?

I don't think it should take a lot more power. When you increase the diameter of a propeller you get a greater thrust yield for the same power. If you think of a wing as huge propeller, then you can see how it would be able to generate highly efficient thrust.

Yeah! It is possible to build an aircraft that flaps its wings to fly, but the fuel efficiency, complexity of design and cost required for that flight would be a burden to implement. This has been attempted in the past, but virtually all designs have failed, mostly for mechanical reasons.
The commercial aircraft and their working principles are a far more satisfactory design to carry payload in a cost-effective manner. An ornithopter design, were it successful, would require more energy and mechanical complexity to carry even a small payload.


text:
When does the overspeed alarm goes off in a plane?
I want to know when does the overspeed goes off in aircraft. How exactly is overspeed limit decided? Is it fixed for all the situations, or does it keeps changing? In a game that I play, (Infinite Flight) it goes off at 350 knots air speed for a Bombardier CRJ 200 or Cessna Citation X. But, it seems unrealistic as real planes often easily fly over 450 knots air speed.

It goes off when the aircraft exceeds Vne. Vne is different for different aircraft, so without knowing specifically what aircraft you are talking about I can't tell you if it is realistic or not. Some jet aircraft can't go that fast, so it would be reasonable to hear it...

@RonBeyer Or max Mach (Mmo). Mmo vaties with air density.

@JonathanWalters Very true! I'm not sure if Vne changes with Mmo or if it always stays the same. I had assumed that Vne (with respect to the warning sound) would vary based on conditions like air density and even aircraft configuration (like Vfe or Vle).

@RonBeyer Aircraft that fly at higher altitudes will typically have both a Vmo and Mmo limitation. Vmo limitations will be expressed as KIAS, while Mmo will be expressed in Mach number. Vne does not vary with configuration; other speed limitations define those limits.

On a similar note, I do get yelled "overspeed" in anything over M1.5 in a flight sim in an SR-71 at 45,000.

that's because you're exceeding Vmo at that altitude.  Blackbirds can't/don't fly at Mach 3 until about 70,000 ft or so.

@SMSvonderTann Isn't you being a simulated SR-71 pilot simulated classified information? Careful you don't get your simulated ass thrown into a simulated jail!

You have ground speed and airspeed mixed up. A 747 can only go about 310 knots per whatever while its ground speed can go up to like 575 or something like that while its up at 30000 feet

The overspeed goes off when either the indicated airspeed exceeds that limit or the mach speed exceeds the mach limit. At least that's how it worked on 747-100/200 aircraft.
The 350 knot figure for the max operating airspeed sounds reasonable to me as long as you're low. From memory that was around the max operating INDICATED airspeed for 747-100/200 aircraft. Remember, though, that indicated airspeed decreases with air density. A 747 cruising above 30,000 feet at around 550 knots TRUE airspeed is going to show an indicated airspeed of less than 300 knots. However, that cruising true airspeed of 550 knots or so is going to be around mach 0.86. The max mach number for the 747 was 0.92.
If you were at, say, 15,000 feet and speeded up to 350 knots, the mach number would be much less than 0.86.
Take your sim up to 35,000 and see what you get.

The overspeed clacker on the CRJ 200 series will sound "at" a calculated limit speed which is either VMO or MMO (depending on altitude) according to the documentation available at smartcockpit.com . The Cessna Citation X is similarly limited "at" VMO or MMO.  You can find these numbers on other answers.
One thing to keep in mind is the difference between true air speed and indicated airspeed/calibrated airspeed.  At a constant indicated air speed, the true air speed (the speed with which you're physically moving through the air) will be higher at higher altitudes and higher temperatures. However, the speed limits are aerodynamic numbers and are given as indicated airspeed numbers, because despite changes in altitude and pressure the limits stay at the same indicated air speed.  Therefore, if VMO is 350 knots you can go faster than 350 knots true airspeed, but only at a high enough altitude where your indicated airspeed is still lower than 350 knots.  For example, at 20,000 ft. MSL I can go 450 kts. true airspeed without going above 350 knots indicated airspeed.
VMO is used in place of MMO when VMO is lower.  When the airplane is at a low enough altitude, a constant IAS is used for the limit and at higher altitudes the calculation is done instead in mach, as shown in the diagram below.  Note that the horizontal axis is in knots indicated airspeed, not Mach number or true airspeed.
Sample VMO vs MMO chart from "Aircraft Trajectory Tracking by Nonlinear Spatial Inversion" at Research Gate
Now, I say "at VMO" in quotation marks because often this calculated limit speed is offset slightly above the VMO/MMO so you can fly at exactly the VMO/MMO without the alarm going off.  (See this Aviation Today article for examples from Airbus). There is also sometimes logic to detect and warn about imminent overspeed events.  When accelerating rapidly, these warnings will go off slightly before the normal VMO/MMO alarm would.  The Cessna Citation X has similar behavior, but it does not seem to affect the overspeed warning horn: "When the airspeed trend vector exceeds VMO by one knot, the rolling digits turn amber unless a red indication is called for."
Many planes also have a similar speed where an overspeed protection feature in the flight guidance system activates (similar to stall-preventing underspeed-protection modes), but I couldn't find anything listing such a feature for the CRJ 200 series.  There is a warning saying that some modes can command the CRJ 200 to exceed VMO/MMO if used improperly, so I don't think it uses VMO/MMO to limit flight director commands. The Cessna Citation X flight guidance system does not behave like the the CRJ 200, and will limit commands "to VMO/MMO" according to the manual for the Citation X Model 750 at smartcockpit.com  So the Citation X does have a speed protection feature, but according to the documentation I can find this also activates "at VMO/MMO."
Note that for both jets this speed is dynamically calculated by the avionics based on configuration (extending flaps and lowering landing gear decrease the VMO).  For example, the Cessna Citation X has the following VMO speeds listed for the Model 750:
╔═════════════╦═════════════╗
║   Config    ║ Speed Limit ║
╠═════════════╬═════════════╣
║ Flaps 5°    ║ 250 Knots   ║
║ Flaps 15°   ║ 210 Knots   ║
║ Flaps > 15° ║ 180 Knots   ║
║ Gear Down   ║ 210 Knots   ║
╚═════════════╩═════════════╝

I can't find a VNE for them but a post on Airliners.net lists the VMO, which is the fastest you're supposed to fly it in cruise, for the CRJ200 as:

0 - 8000ft 330kts
8000ft - FL255 335kts
FL255 - FL280 M0.80
FL280 - FL316 315kts
FL316 - FL410 M0.85

This AOPA article lists the VMO of the Citation X as Mach 0.92, or 547 KTAS. The corresponding IAS would depend on altitude and temperature. From the same article the updated version, called the Citation X+ the speeds are listed slightly higher:

VMO (max operating speed) at sea level to 8,000 ft | 270 KIAS
VMO (max operating speed) at 8,000 ft to 30,650 ft | 350 KIAS
MMO (max Mach number) | 0.935 M*

* At 30,650 0.935M would be 549 KTAS

Interesting that for the CRJ2 the limit goes back to knots at FL280 before going back to a different Mach at FL316.

@fooot That is weird. I hadn't noticed that before. Those numbers came from somebody who posted them on Airliners.net, so there's no certainty that they're accurate

From my experience with private jets there's a single fixed Mmo so those values look off to me too.

I would like to add a bit of explanation for why the rules for $V_{MO}$ are so complex:
There are three different phenomena that limit the maximum speed of an aircraft:

The direct pressure peeks and minima that stress the structure. These are proportional to the dynamic pressure, which is measured as indicated airspeed (well, equivalent airspeed). At certain indicated speed, the pressures will be more than the structure was built for and you risk damage, so there is maximum operating speed, $V_{MO}$.
Indicated
airspeed is proportional to the air density and square of speed. At sea level it is numerically equal to the true airspeed, but high up in the typical cruise levels you can have 460 knots true with just, say, 270 knots indicated and Mach 0.80 (the actual values depend on altitude and on pressure and temperature on the day).
Every structure is to some extent flexible and has a resonant frequency. The turbulence around the structure creates pressure oscillation with its own frequency and this frequency decreases with speed. At some speed, the frequency will match the resonant frequency of the structure, which will cause aeroelastic flutter.
Since the frequencies depend on true airspeed, there is a maximum for that as well. But because instruments in aircraft only show indicated airspeed, there is instead a table or graph showing decreasing $V_{MO}$ with altitude.
In modern aircraft, the table is built into the flight management system, so the $V_{MO}$ for current altitude is shown on the airspeed indicator and the alarm is sounded when it is exceeded.
When the flow around the wing exceeds the speed of sound, the pressure field changes, shifting the centre of lift aft, which causes pronounced pitch-down moment. Aircraft not designed for supersonic flight may not have enough elevator authority to compensate for this, so a loss of control might result.
This depends on Mach number (ratio of true airspeed to speed of sound). Since speed of sound only depends on temperature, for aircraft that fly in transsonic regime, a $M_{MO}$ is usually selected so that it covers both this and flutter at temperatures that can be expected at the cruise altitudes, simplifying the logic a bit—you only have a $V_{MO}$ and $M_{MO}$ and up to some altitude, you reach $V_{MO}$ first and above it you reach $M_{MO}$ first.

Additionally, there is usually $V_{MO}$/$M_{MO}$, maximum operating speed, and slightly higher $V_{NE}$/$M_{NE}$, never exceed speed. This is mainly about safety margin. The maximum operating speed is what you should stick to. If you reach the never exceed speed, your safety margins are getting really thin.


text:
Why was F-18 chosen to escort Space Shuttle Endeavour?
This question is kind of a continuation to Why does NASA have F/A-18s?
The accepted answer states that

"NASA uses them for pilot training and as chase planes for research
  aircraft."

So, why was F/A-18 chosen for the Space Shuttle, among ton of other options available (all aircraft with 2 seats)? Also, I would like to know why NASA got F/A-18 in the first place, out of the rest.

Because that's what NASA had at the time.

Because it's what they had at the time and it's what the astronauts were flying. Only one of the NASA F/A18's is actually a two seater:

The aircraft were obtained from the U.S. Navy between 1984 and 1991.
  One has a two-seat cockpit while the others are single-seat aircraft.
  NASA research support aircraft are commonly called chase planes and
  fill the role of escort aircraft during research missions.

Their main purpose is to keep an eye out for external issues with the carrier. This podcast covers most of the nitty gritty details of that operation.

Chase pilots are in constant radio contact with research pilots and
  serve as an "extra set of eyes" to help maintain total flight safety
  during specific tests and maneuvers. They monitor certain events for
  the research pilot and are an important safety feature on all research
  missions.

As for why they have them:
NASA has a long history of using high performance jet trainers to keep the astronauts sharp. Since many of the older generation of shuttle pilots came out of the Navy or were test pilots, choosing former Navy aircraft is only logical. For much of the Apollo era as well as the shuttle era they actually used T-38's for training and keeping the astronauts current. NASA likes high performance, safe, simple jets for astronaut training as there are things you encounter actually flying that you just don't in the simulator.

"It's actually our most important training that we do as astronauts,"
  said Terry Virts, who flew as the pilot of STS-130 aboard shuttle
  Endeavour. "It’s the one place where we're not in a simulator. It's
  real flying and if you make a mistake, you can get hurt or break
  something or run out of gas. There are a lot of things that happen
  real-world in a T-38 that don't happen in the simulator."

The actual shuttle trainer is a GII that flies with the gear down, full flaps, and thrust reversers to simulate the descent of the shuttle.

Back when the first Mercury astronauts joined NASA, nobody knew where the space program would take them. They took a major risk, and as part of the deal they would follow the same career progression as active-duty pilots, including modern jet aircraft and regular training to stay current in the cockpit.

NASA has a lot of aircraft that it uses for all kinds of things. Many of those were military aircraft that have had their weapons and such removed. They're still very high performance aircraft, much better than anything civilian, and that has pretty obvious appeal to NASA. In the original post, the F-18's appear to be an escort for a photo op.
NASA has used a variety of aircraft as chase planes, including the F-5 and T-38. NASA has also done research using the F-15 and F-16.
I'd guess the use of the F-18 has something to do with maintaining a somewhat common fleet with the Navy, to ensure the future availability of parts and spares. But I can't say for sure.

I'd expect better performance than the military versions, too, with the weight of the weapons systems removed.

@jamesqf quite likely those systems, if removed, were replaced with ballast to keep the balance of the aircraft intact. Or were replaced with mission appropriate equipment like extra cameras or sensors of course. Combat aircraft for the same reason tend to behave best when they have a full load of ammunition for their internal weapons, and for example the F/A-18 is from what I've heard a bit tail heavy when flying without it.